1. Field of the Invention
The present invention relates to a light emitting module that converts a wavelength of the light emitted from a light emitting element, and more specifically, it relates to a laser emitting module that uses a laser diode, a window cap and a laser pointer using the laser emitting module.
2. Description of Related Art
In order to point a referring portion on a screen during a presentation or the like, a pointer capable of emitting a spot light is used. This type of pointer, as it uses a spot light for pointing the referring portion, has such advantages that it can point out any portion on the screen from a distance, and with easier in handling than a rod-like pointer, as it is provided in a compacter size. In order to explicitly point out an intended portion on the screen irrespective of a distance between the user and the screen, it is preferable that the light emitted from the pointer is non-divergent and illuminates only a limited area. Accordingly, use of a laser beam emitted from a semiconductor laser is preferable.
A semiconductor laser used in a typical laser pointer is mainly of a red light emitting laser diode, and in many cases, red color light close to infrared is used. Its relative visibility factor is low. Thus, in order to improve its visibility, an output level of emission thereof must be increased. On the other hand, as it is likely to be concentrated on a very small area, it has been desired for its output to be limited within a safe level at which no injury would occurs to human body even if the laser beam happens to directly enters human eyes. For laser beams having wavelengths in a range from 400 nm to 700 nm, according to the “Laser Beam Injury Prevention Guidelines”, its output is desired to be limited below 1 mW.
If the output is limited below 1 mW, because of the low relative visibility for the laser beam emitted from the red light laser diode, it becomes difficult for human eyes to discern the indicated position which is being illuminated by the pointer during presentation using a projector. Accordingly, as an alternative laser pointer using a laser beam in a range of wavelengths which can provide a higher relative visibility factor than the red light, another type of laser pointer has been proposed. For example, Japanese Patent Application Publication H06-326380 discloses an optical resonator including a solid state laser medium which is excited by a laser emitted from a laser diode and a non-linear optical element which converts a wavelength of light generated by excitation of the solid state laser medium, which are sandwiched between dichroic coats, for outputting a laser beam having a wavelength shorter than red light.